I have multiple string values, I want to insert in an sql server db table, But i want to check values one by one if it already exist in the db I will update, if not I will insert it.
I am using Entity Framework 4.1, and I hope I can do that with best performance, means less calls to db as I can.
I saw this question before, but they are using linq to sql not entity framework.
One way you could do it is to batch up the queries for existence ... for example, using the .Contains method (like this), you can query for some or all of the items which may or may not exist at once. Then once you have the data locally, you can quickly check if it's there before inserting
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I am working on my first project using an ORM (currently using Entiry Framework, although that's not set in stone) and am unsure what is the best practice when I need to add or subtract a given amount from a database field, when I am not interested in the new value and I know the field in question is frequently updated, so concurrency conflicts are a concern.
For example, in a retail system where I am recording a sale, as well as creating records for the sale and each of the line items, I need to update the quantity on hand of the items sold. It seems unnecessary to query the database for the existing quantity on hand, just so that I can populate the entity model before saving the updated quantity - and in the time taken for that round-trip, there is a chance that the same item will have been sold through another checkout or the website, so I either have a conflict or (if using a transaction) the other sale is blocked until I complete my update.
In SQL I would simply write
UPDATE Item SET Quantity=Quantity-1 WHERE ...
It seems the best option in this case is to fall back to ADO.NET + stored procedure for this one update, but is there a better way within Entity Framework?
You're right. ORMs are specialized in tracking changes to each individual entity, and applying those changes to the DB individually. Some ORMs support sending thechanges in btaches, but, even so, to modify all the records in a table implies reading them all, modifyng each one, and sending the changes back to the DB as individual UPDATEs.
And that's a big no-no! as you have corectly thought. It implies loading all the rows into memory, modifying all of them, track their changes, and send them back to the DB as indivudal updates, which is way more expensive that running a single UPDATE on the DB.
As to the final question, to run a SQL command you don't need to use traditional ADO.NET. You can run SQL queries directly from an EF DbContext using ExecuteSqlCommand like this:
MyDbContext.Database.ExecuteSqlCommand('Your SQL here!!');
I recommend you to look at the MSDN docs for Database class, to learn all the things that can be done, for example managing transactions, executing commands that return no data (as the previous example) or executing queries that return data, and even mapping them to entities (classes) in your model: SqlQuery().
So you can run SQL commands and queries without using a different technology.
I use MS data access application block for interaction with database and I saw its performance is good. When I like to add 100 or more records then I send those 100 records in xml format to a stored procedure and from there I do a bulk insert. Now I have to use Entity Framework. I haven't ever used EF before so I am not familiar with EF and how it works.
In another forum I asked a question like "How Entity Framework works in case of batch insert and update data" and got answer
From my experience, EF does not support batch insert or batch update.
What it does is that it will issue an individual insert or update statement, but it will wrap all of them in a transaction if you add all of your changes to the dbcontect before calling SaveChanges().
Is it true that EF can not handle batch insert/update? In case of batch insert/update EF inserts data in loop? If there are 100 records which we need to commit at once then EF can not do it?
If it is not right then please guide me how one should write code as a result EF can do batch insert/update. Also tell me the trick how to see what kind of SQL it will generate.
If possible please guide me with sample code for batch insert/update with EF. also tell me which version of EF support true batch operation. Thanks
Yes EF is not a Bulk load, Update tool.
You can of course put a a few K entries and commit (SaveChanges)
But when you have serious volumes of speed is critical, use SQL.
see Batch update/delete EF5 as an example on the topic
I am looking into adding history tables to my database. The easiest way is to intercept all Insert, Update and Delete calls that EF Makes and add in a merge that will also insert a history row into a history table.
Right now all my Entities just let EF figure out how to do the inserts, updates and deletes.
If I go and add in stored procedures (instead of the EF Generated stuff) will EF still function the same on the business tier?
Or does it change how I have to work with my entities? If so, how?
Everything works the same, it is transparent.
Stored procedures need to return the rows affected, in order for EF to know that the update succeeded or not. Additionally, if you do an update and need to map any property back to your entity (e.g. timestamps) you must select them in the sproc and then map them back in the EF designer (since you can only have one output parameter, and that should be the rows affected).
You might consider using triggers on the DB to solve your issue, though?
Doing this in stored procedures means that you will write all inserts, updates and deletes yourselves. It is like throwing 30% of feature set (and 50% productivity) away. Create audit records in your application and save them together with main records through EF.
We have an application that creates new tables at runtime, but always with the same table schema. The only thing that varies from one of these tables to the next is the table name. Is it possible to access these tables using Entity Framework, specifying which table to access by name?
Entity Framework is not designed for DDL, it's an ORM tool for data access. You would want to use a simple ADO.NET query to create/drop the table.
Creating and dropping tables for every user session will make your log file grow very big very fast. I would consider carefully the reasons you think this is necessary. If the data is temporary, why not save the Session ID in each row and truncate the table on a daily basis?
UPDATE:
No, not really. The Entity Data Model is not dynamic, it's a static XML document that describes the structure of the database. If you want to interact with a table with a dynamic name, you're going to have to stick to "classic" ADO.NET.
With Linq to SQL I guess it would be possible with a stored procedure taking the table Name as a parameter.
A nice post about SP in L2SQL: http://weblogs.asp.net/scottgu/archive/2007/08/16/linq-to-sql-part-6-retrieving-data-using-stored-procedures.aspx
I don't know if that feature exists in EF.
What's the correct syntax of a JPA insert statement? This might sound like an easy question but I haven't been able to find an answer.
I know how to do it from Java code but I'm looking for a way to insert objects into the database if the database was created.
Any ideas?
There is no INSERT statement in JPA. You have to insert new entities using an EntityManager. The only statements allowed in JPA are SELECT, UPDATE and DELETE.
Here is a good reference on persisting JPA objects using an EntityManager. As an example, this is how to insert objects using the persist method:
EntityManager em = getEntityManager();
em.getTransaction().begin();
Employee employee = new Employee();
employee.setFirstName("Bob");
Address address = new Address();
address.setCity("Ottawa");
employee.setAddress(address);
em.persist(employee);
em.getTransaction().commit();
If you want to insert data to the database outside java you need to use native SQL. Use SQL Standard to make sure most databases can execute the script. When the application runs, JPA will make the mapping of the new data and convert it into objects when needed.
How to make sure the script works in all databases? well thats the same problem any DBA has when making Store Procedures or native queries... thats why JPA exists, to avoid making it directly in SQL, but I know sometimes is needed that way.
I suggest you to make 3 main scripts. One for Oracle, one for SQL Server (there are some issues in the date datatypes from 2005 to 2008 versions so be careful) and one for MySQL. Start your script with standard SQL and when you test it in this databases you will find some fixes you will need to do for each DBMS.
One you got it you can make a file script (*.sql) file and run it with the DB manager. If it works run the server, put the app online and the data will be integrated just fine.
The option that looks more promising so far is using Flyway. It is a more automated way of doing it and handles the upgrade process of databases basically automatically.
No need to write a separate INSERT query in JPA. JpaRepository has inbuilt saveAndFlush() method which you can use to insert into the database. Hope this works for you.